The invention relates to a transceiver which can be connected to a baseband circuit of a mobile phone via bidirectional internal interface lines.
By way of example, cellular mobile radio networks operate according to the GSM standard (GSM = global system for mobile communications). In a time division multiplex mode (TDMA = time division multiplex access) useful data are transmitted within so-called time slots. Conventional mobile phones have a modulator for transmitting the data and a demodulator for receiving the data.
German patent application DE 197 19 658 A1 describes a transceiver for radio-frequency channels. The transceiver has a baseband circuit which is fed in the reception mode by a demodulator and in the transmission mode feeds a quadrature modulator. At the antenna end, a changeover switch is provided for switching over between the transmission path and the reception path.
German patent DE 195 28 069 C2 describes a radio unit with a signal processor. In a reception mode, the signal processor is fed by a demodulator. In a transmission mode, the signal processor feeds a modulator. A controller serves to switch over an antenna-end changeover switch so that, depending on the mode of operation, either the reception path is activated by means of the demodulator or the transmission path is activated by means of the modulator. The control signals which are output by the controller are also fed to the demodulator and the modulator.
FIG. 1 shows the structure of a conventional mobile phone as in the prior art. Via a reception line RX, a demodulator D receives reception data which are fed to an analog/digital converter A/D via an in-phase line I, an inverted in-phase line {overscore (I)}, a quadrature-phase line and an inverted quadrature-phase line {overscore (Q)}. The A/D converter converts the analog signals into digital data and outputs it to the digital baseband circuit B of the mobile phone. Conversely, in the transmission mode the digital baseband circuit outputs the data to a digital/analog converter D/A which converts the digital data into analog signals and forwards them to a modulator M via an in-phase line I, an inverted in-phase line {overscore (I)}, a quadrature-phase line Q and an inverted quadrature-phase line {overscore (Q)}. The modulator M generates a modulated transmission signal as a function of the received analog signals, and outputs the modulated transmission signal via a transmission line TX.
In conventional mobile phones, the modulator M and the demodulator D are integrated in a single circuit S1, while the baseband circuit B is integrated with the analog/digital converters and the digital/analog converters in a circuit S2. As shown in FIG. 1, the two integrated circuits S1, S2 are connected via a total of eight interface lines if a quadrature modulation method as in the case of GSM is used.
The integrated transmission and reception circuit S1 has not only the demodulator D and the modulator M but also a multiplicity of further, non-illustrated components which are required for the transmission and reception modes. The components include, for example, PLL circuits, voltage-controlled oscillators, and voltage-regulation switching devices. These components are connected by means of a multiplicity of non-illustrated control lines to the baseband circuit of the mobile phone on the one hand, and to the transmission stage and the reception stage on the other hand. Furthermore, the integrated circuit S1 requires housing terminals or pins for connection to the supply voltage and to ground. Owing to the desired miniaturization, the number of available housing terminals in the integrated circuit S1 is, however, limited. For this reason, owing to the insufficient number of available housing terminals, desired ground connections are dispensed with in conventional transceivers for mobile phones, as a result of which the operating properties are degraded.
A further disadvantage of transceivers in conventional mobile phones is that the high number of interface lines to the baseband circuit leads to a high level of susceptibility to interference because the useful data which are easily falsified by external influences are transmitted on these lines. For this reason, these interface lines have to be shielded in a costly fashion and protected against interference using capacitors. This leads, on the one hand, to increased costs in manufacture and at the same time restricts the possibilities of further miniaturization of the mobile phone.
The object of the invention is to provide a transceiver which overcomes the above-noted deficiencies and disadvantages of the prior art devices of this general kind, and which can be connected to a baseband circuit of a mobile phone with as few interface lines as possible.
With the above and other objects in view there is provided, in accordance with the invention, a transceiver selectively operable in a transmission mode and a reception mode, the transceiver comprising:
bidirectional internal interface lines for connection to a base circuit;
a quadrature modulator connected to the bidirectional internal interface lines in a transmission mode of the transceiver; and
a quadrature demodulator connected to the bidirectional internal interface lines in a reception mode of the transceiver.
In other words, the transceiver according to the invention has bidirectional internal interface lines which can be connected to a baseband circuit of a mobile phone, the transceiver being capable of being switched over between a transmission mode and a reception mode by the baseband circuit, and at least one quadrature modulator which in the transmission mode is connected to the interface lines via transmission lines, and has at least one quadrature demodulator which in the reception mode is connected to the interface lines via reception lines.
In an advantageous refinement of the transceiver according to the invention, the quadrature demodulator is switched to high impedance in the transmission mode, and the quadrature modulator is switched to high impedance in the reception mode.
This provides the particular advantage that the interface lines can be operated in both directions without the frequency response of the quadrature demodulator being influenced by the quadrature modulator in the reception mode, and conversely the frequency response of the quadrature modulator is not influenced by the quadrature demodulator in the transmission mode.
In accordance with an added feature of the invention, the quadrature modulator and the quadrature demodulator are electronically completely isolated from one another.
In accordance with an additional feature of the invention, a multiplex switching device is connected between the internal interface lines and the quadrature demodulator and a multiplex switching device is connected between the internal interface lines and the quadrature modulator. When the transmission and reception lines are switched by means of multiplex switching devices, the result is a particularly advantageous switching over between transmission mode and reception mode which is effected quickly and reliably with little circuit complexity.
In accordance with another feature of the invention, a multiplex control circuit is connected via internal control lines to the multiplex switching devices. Furthermore, there may be provided a control line for connecting the multiplex control circuit to the baseband circuit of the mobile phone. This provides the particular advantage that the switching over between transmission mode and reception mode can be controlled by the baseband circuit via a single control line, with the result that only one housing terminal pin of the transceiver is required to do so.
In accordance with a further feature of the invention, the transmission and reception lines each include in-phase and quadrature-phase lines.
In particular, the transmission and reception lines each include an in-phase line, an inverted in-phase line, a quadrature-phase line, and an inverted quadrature-phase line.
In accordance with again an added feature of the invention, the modulator is a GMSK modulator and the demodulator is a GMSK demodulator.
In accordance with a further alternative of the invention, the modulator is a QAM modulator and the demodulator is a QAM demodulator.
In accordance with again another feature of the invention, the modulator is a PSK modulator and the demodulator is a PSK demodulator.
In accordance with again a further feature of the invention, the transmission and reception modes of the transceiver are each maintained at least for a duration of a time slot of a TDMA data channel access.
In accordance with a concomitant feature of the invention, the above-outlined transceiver is utilized as a transmitter and a receiver for the baseband circuit of a mobile telephone.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in transceiver with bidirectional internal interface lines, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.